The invention relates to a circuit arrangement for producing a D.C. current.
For electronic circuit arrangements to be inserted into battery-operated devices, a lowest possible energy consumption is to be aimed at for economic and ecological reasons. Therefore, electronic circuits which are designed for operation with low supply voltages and low power consumption when in operation have become very important for such devices. In this respect, the energy supply provided by only a single battery cell is aimed at while a D.C. voltage converter for increasing the supply voltage is dispensed with. Under these conditions, an electronic circuit whose voltage is supplied in this manner is to remain operable without any limitations even with a supply voltage down to about 0.9 volt, while the nominal value of the supply voltage is set to 1 volt, for example. When taking the fact into account that for bipolar transistors the base-emitter voltages in the conductive state are typically about 0.7 volt, there is the necessity for the use mentioned above to create specific circuit configurations because, for example, many transistor circuits are capable of operating only with considerably higher supply voltages.
In many applications it is necessary to have stabilized D.C. currents as current references, while these stabilized D.C. currents are to be independent of variations of the supply voltage, so that, for example, variations of the voltage produced by the battery, caused by different charging conditions of the battery must not have any influence on the function of the powered electronic circuits.